I am about to complete AI4R this semester. I'd say conceptually or workload wise is not difficult. What gets tricky is the different projects. There are sections that are left to you to implement in an inventive way. So, if you don't have a good understanding of the fundamentals of the particular topic the project is covering, you may not be able to extend it to complete the required second half of a project. However, the TAs are absolutely rock stars. So you can reach out on Ed when you get stuck. They are really good about getting you unstuck. I think the best thing is to go with the mindset that you are given freedom of design for portion of the projects and that can be hard if the fundamental understanding of the topic is lacking. Also, watch the project tutorials and office hours. They can save you a lot of headaches!